Photo courtesy of Living Roofs Inc.

The construction of new buildings is a given – but their styles and forms are not. Design sensibilities are constantly changing, and the green industry is rapidly taking notice of one trend in particular: green roofs.

Elevated gardening is not a new concept. People have been planting gardens on rooftops for decades, but the practicality and appeal of green roofs, which function similarly to a yard planted on the roof of a building, are catching on with architects, landscapers, urban planners, homeowners and more.

To plant a green roof or living roof, a waterproofing membrane is built into the surface of a building’s roof (or wall to create a living wall) and a growing medium is layered over the membrane, in which ornamental grasses, turf and other plants can be grown. This provides extra color, life and vibrancy to new and existing structures, and can also enhance the rain water drainage capabilities of the building.

Coinciding with the increasing popularity of urban gardens, green roofing is gaining favor with planners and landscapers alike. Ed Snodgrass, president and owner of Green Roof Plants in Maryland, says the perception of green roofs has certainly changed during the past 10 to 20 years.

“It’s not been parabolic growth, but if I look all the way back to 1999 or something, there would be no one on architecture boards who would have a green roof,” Snodgrass says. “Now, I think, almost all flat-roof commercial buildings probably start with a green roof, and it has to be taken out (of the plan) for financial reasons or structural loading. They are part of the conversation now, so that marketing hurdle has been crossed.

Green roofs, or living roofs, are gaining popularity as a method of beautification and storm water filtration on new and existing structures.
Photo courtesy of Living Roofs Inc.

“Roofers used to say, ‘I’ve spent my whole career trying to move water off the roof and now you’re trying to hold it?’ Now, roofers are some of the biggest advocates,” Snodgrass says.

However, the growth of green roofs is determined in large part by government action and public policy, which varies drastically between counties, states and countries.

Rule of law.

Around the world, national leaders are recognizing the importance of green space to the point that in some countries, green roofs are expected for buildings of a certain size, Snodgrass says.

“Green roofs, no matter which country they’re in, are going to go as far as public policy pushes them,” he says. “If there’s a robust public policy, like in Germany (where various tax credits heavily incentivize green roof construction) … we’re not quite there in the U.S., and our jurisdictions are not national. Building codes are local in the U.S., so each market might have a different way to incentivize a green roof or to require it.”

“Green roofs, no matter which country they’re in, are going to go as far as public policy pushes them.” Ed Snodgrass, owner, Green Roof Plants

Some American markets and regions are beginning to catch on to the positive aspects of green roofs, says green roof system installer Kate Ancaya. Along with her husband, Emilio, Kate is co-founder and operator of Living Roofs in Asheville, North Carolina, a company that also specializes in living walls.

“Cities like Washington D.C., Philadelphia, Pennsylvania, and Portland, Oregon, are demonstrating how green roof policy influences the quantity and quality of green roofs,” she says. “It is our hope that other municipalities will pay attention and adopt their own green roof policies.”

The city of Philadelphia’s water department encourages green roof construction by offering a tax credit to businesses that install green roofs and advises homeowners that they can reduce their storm water treatment bills by doing the same.

This push for treatment of storm water by running it through soil is possibly the beginning of a greater trend toward biological filtration, Snodgrass says. As with many new technologies, green roofs are being incentivized by governments for now, but at some point, businesses will start to see the business sense on their own, he says.

“It will be driven by government in terms of investment because businesses don’t invest more than they have to, but eventually, the system gets cheaper,” Snodgrass says. “It’s like the solar panel thing 20 years ago. Now, you see Apple and Google and Oracle building their own power plants for themselves. They don’t need the incentive because they say, ‘Oh, energy independence. Yeah, we’ll take that.’ I think the same thing will happen with biological water filtration.”

The right plants for the job.

Although impressions of green roof technology are moving in a positive direction, professionals involved in their design and implementation warn against jumping into such projects unprepared. Ancaya says that green roofs face a much different set of challenges than a traditional lawn or garden.

“It is important to understand the conditions on a roof are very different than the conditions of an at-grade landscape,” she says. “Roofs are typically harsh environments with extreme wind, heat, exposure and limited soil depths.”

Additionally, too many green roof installers fail to take the time to consider which plants fit the environment of the roof they’re working on, Snodgrass says. Coming from a growing background before getting involved in green roof consulting, he knows to think about what will survive on the roof, thrive in the region’s climate and provide lasting value.

Experts say green roof installers should heavily consider the local environment when deciding on which plants to use.

“I think there’s a real push by some manufacturers to use the same plants everywhere in the U.S. So, it’s a funny thing coming from a horticulture and plant background … and all the contractors … just want to say, ‘Here’s what worked in New York, and we’re doing a project in Phoenix, so why don’t we just do the same thing there?’

“There’s that hurdle to cross yet, where the systems (should be) really optimized horticulturally for that locale,” Snodgrass says. “That’s what we’ve been focused on. I think plant people want the right plant in the right place, generally.”

Another consideration that plant people can bring to the green roof process is the question of what a business or homeowner wants to accomplish with their green roof. Goals can range from storm water treatment and mitigation to pollinator-friendly gardens to pure ornamental landscapes.

“It is important to understand the conditions on a roof are very different than the conditions of an at-grade landscape.” Kate Ancaya, co-founder, Living Roofs

“We have found that some homeowners are most excited about environmental benefits while others are pleased with the economic benefits,” Ancaya says. “For a homeowner looking out onto their green roof, they have the added appeal of the aesthetic quality of a green roof.”

Whatever a client wants to do with their green roof, Snodgrass says it all comes down to knowing what different plants are capable of and how they can be used.

getting input.

Landscaping experts are seeing an opportunity to apply their skills in the green roof market, but they don’t have to do it alone.

Snodgrass says that with more homeowners adding onto their homes and asking their architects to incorporate green roofs into the design/build process, there’s an indication that the trend could start to be applied in smaller-scale projects around the home.

Customers building a green roof on their house will most likely go to a contractor for the plants they’ll need, but a local retailer could help a contractor and a customer plan out a living wall for the side of a house, for example.

“I think you’re looking at the retail level – it’s something where you could use green roof technology but on a homeowner’s scale,” Snodgrass says.

“Whether that would be birdhouses, doghouses, dish gardens or xeriscaping. It’s saying, ‘Well, if I’m going to put something on the roof and it’s going to grow in 4 inches of non-irrigated media, also I have this hillside in my property’ … you can use that same technology to solve other residential problems.”

Contractors can also look to their suppliers as possible customers because green roofs can be an asset for a garden center.

When retailers improve or update their facilities, it’s worth it for them to consider a green roof or living wall for their building.

Some cities in the U.S. offer tax incentives to businesses that incorporate green roofs into their construction plans.

Such a move toward extra greenery can brand the business and signal to the world: This company is in the business of plants.

“It becomes another billboard for them,” Snodgrass says. “If you’re driving down the highway and you see a roof – especially if it has a little pitch to it – full of plants, your eye is going to go to that. ‘Oh, that’s a garden center!’ And you may not have even seen the sign that says ‘garden center.’”

Time will tell where the green roof trend will lead, but as with any investment, green roofing will not be a simple matter of spending or even market research.

An investment of personnel and knowledge is also critical for retailers interested in living roofs and walls.

“It’s not just the plant any more,” Snodgrass says. “It’s not for the garden center that just wants to plop down some plants and think it’s going to happen.

“You’re going to have to invest the intellectual capital in these lines if you want to get into it.”